In this blog post, based on Thomas S. Kuhn’s ‘The Structure of Scientific Revolutions’, I will examine the nature of the scientific revolution and explore whether the paradigm shifts observed in the actual history of science were truly discontinuous changes significant enough to be called revolutions.
Since its publication, Thomas S. Kuhn’s ‘The Structure of Scientific Revolutions’ has established itself as a best-seller representative of the late 20th century and has had a profound influence on our understanding of the structure of the history of science. His work has had a wide-ranging impact not only on the history of science but also on various fields such as the philosophy of science and the social sciences. In ‘The Structure of Scientific Revolutions’, Kuhn explains that science develops through the following process:
Existing paradigm (normal science) → Emergence of a crisis → New paradigm through revolution
Since the scientific revolution described by Kuhn bears similarities in many respects to social revolutions such as the dismantling of feudalism, the term “revolution” is naturally accepted. Kuhn viewed normal science as inherently cumulative, but saw a scientific revolution as an event that disrupts that continuity. According to his explanation, when an existing paradigm faces a crisis, various alternative ideas emerge; once the scientific community selects a new paradigm from among them, the existing normal science collapses, and problems are solved anew under the new paradigm. In other words, the scientific revolution described by Kuhn is a rapid and fundamental change that radically shakes up the existing system.
However, when examining the actual process of paradigm shifts in the history of science, we find that it differs somewhat from the scientific revolution described by Kuhn. In many cases, actual paradigm shifts are far more gradual and continuous in nature than Kuhn suggested. In what follows, we will examine this gradual nature, which emerges during the transitional period of paradigm shifts, through specific examples.
Achievements that are adopted as paradigms must meet the following conditions.
First, they must be sufficiently original to lead a community of scientists—who are committed to existing research—in a new direction.
Second, it must offer open possibilities sufficient to continuously present a variety of problems for the newly formed research community to solve.
Kuhn explained that Einstein’s theory of relativity transcended the paradigm of Newtonian mechanics and established itself as a new paradigm. In other words, accepting the theory of relativity required revising the existing view that Newtonian mechanics was an absolutely correct theory. However, even today, Newtonian mechanics remains a core subject in physics and engineering education, and many engineers and scientists actively utilize it in practical calculations and design processes.
This is not because the theory of relativity completely refuted Newtonian mechanics, but rather because it demonstrated that Newtonian mechanics is an excellent approximate theory under certain conditions. In most realistic situations—where an object’s mass is not extremely large and its velocity is sufficiently slow compared to the speed of light—Newtonian mechanics provides a very high degree of accuracy. Under these conditions, the equations of Newtonian mechanics can be derived from the theory of relativity, and the theory of relativity is understood as a more general theory that encompasses Newtonian mechanics. In other words, the theory of relativity can be viewed not as a theory that completely discarded Newtonian mechanics, but as one that broadened its scope of application.
Should we, then, view the theory of relativity not as a new paradigm but as an achievement of normal science within the Newtonian paradigm? Not exactly. The theory of relativity is regarded as a new paradigm because it transcended the existing framework of normal science and proposed new research directions and new problem-solving methods. However, this example demonstrates that paradigms are not completely replaced at a single moment but can coexist for a certain period and undergo a gradual transition.
Although Kuhn emphasized the abrupt replacement of paradigms based on incommensurability, in reality, there are still researchers and engineers today who successfully perform engineering calculations using Newtonian mechanics. They are aware that the scope of application of Newtonian mechanics is more limited than that of the theory of relativity, but they do not deny Newtonian mechanics itself. Rather, they select and apply the theory most suitable for the situation at hand. In this regard, Newtonian mechanics and the theory of relativity have coexisted for a considerable period, and the paradigm shift can be viewed as having occurred gradually. From this perspective, Kuhn’s explanation of the scientific revolution fails to fully reflect the reality of the history of science.
Kuhn argued that rational scientists always choose the superior paradigm. He believed that when a new paradigm emerges, the existing paradigm is effectively pushed out of the realm of science. However, the reality of science cannot be explained so simply. Even today, Newtonian mechanics is taught as a fundamental theory in textbooks and is still widely used in calculating satellite orbits and in various fields of engineering. This is because Newtonian mechanics is not a completely obsolete theory, but rather the most efficient and practical theory under specific conditions.
Scientists do not use Newtonian mechanics out of emotion or inertia. Rather, in situations where calculations are simple and sufficient accuracy can be achieved, there is no need to apply the theory of relativity. In other words, scientists select the appropriate theory by considering not only the relative merits of the theories but also the subject matter, purpose, and computational efficiency. In this regard, it can be argued that Kuhn did not fully reflect the diverse aspects of scientific activity as it occurs in reality and may have somewhat exaggerated the influence of paradigms in his interpretation.
Thus far, we have examined the gradual nature of paradigm shifts, focusing on the differences between the scientific revolutions proposed by Kuhn and those observed in actual scientific history. Through the examples of Newtonian mechanics and the theory of relativity, we have confirmed that a paradigm shift—often referred to as a “scientific revolution”—does not necessarily occur in a discontinuous or abrupt manner. For Kuhn, gradual scientific progress was a characteristic of “normal science” occurring within a single paradigm, whereas a scientific revolution was a non-cumulative process distinct from it. However, looking at actual examples from the history of science, paradigm shifts often occurred over a long period of time, not by completely discarding existing theories, but rather by new theories encompassing or redefining the scope of application of existing ones.
The fact that Newtonian mechanics continues to be used in education, research, and industry even after the emergence of the theory of relativity clearly illustrates this point. Furthermore, the historical fact that Newton’s theory, which emerged in the late 17th century, did not immediately establish itself as a new paradigm but gradually became the standard in the scientific community throughout the 18th century—as many scientists verified and accepted it—also demonstrates that paradigm shifts can occur gradually.
Of course, Kuhn’s concept of “paradigm” provided crucial insights into understanding the development of the history of science and continues to exert significant influence in the philosophy of science today. However, the claim that paradigm shifts always occur abruptly and discontinuously, or that there is incommensurability between different paradigms, has limitations when it comes to explaining all the diverse cases in the actual history of science. Science has evolved through a combination of innovation and continuity, and it is not uncommon for new theories to build upon and expand existing ones rather than completely overturn them. In this regard, it is necessary to consider that a scientific revolution is not only a revolutionary change but also a process of gradual development.
